1. Field of the Invention
The present invention relates to a room temperature curable organopolysiloxane composition for molding purposes, which is used for producing a molding matrix, and which upon curing displays superior mold releasability, particularly relative to unsaturated polyester resins.
2. Description of the Related Art
The production from a master mold of a silicone rubber matrix comprising an organopolysiloxane composition, and the subsequent injection of a material such as a urethane resin, an epoxy resin, a dicyclopentadiene resin or a polyester resin into this matrix to form a resin molded replica product is a well-known technique. In recent years, resin molded products produced in this manner have been supplied for use in automobile components and household electrical components, and the characteristics of such resin molded products are being given serious consideration. As a result, the improvements in the characteristics of the casting resins have been quite dramatic. Unfortunately these improvements have resulted in a deterioration in the durability of the silicone rubber matrix, and the number of replica products that can be produced from a single matrix has decreased. Consequently, improvements in the durability of good mold releasability (hereinafter, referred to as mold release durability) of the silicone rubber matrix with respect to these resins have been keenly sought in order to improve the durability of the silicone rubber matrix and to increase the number of replica products.
It has been disclosed in Japanese Laid-open publication (kokai) No. 9-217009 (JP9-217009A) corresponding to U.S. Pat. No. 6,172,150 that sterically hindered phenols, aromatic amines, and zinc dithiophosphates display superior mold release durability relative to unsaturated polyester resins. Furthermore, a technique for improving polyester mold durability using a radical scavenger is disclosed in Japanese Laid-open publication (kokai) No. 10-279805 (JP10-279805A) corresponding to U.S. Pat. No. 5,814,695. However, these techniques suffer from a problem of unsatisfactory curing of the unsaturated polyester resin at the contact surface with the silicone rubber.